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April 25, 2011 -- A new analysis of data from a major women’s health study finds little evidence that ovary removal during hysterectomy increases heart disease risk.

The findings appear to contradict those from another large study in women suggesting a higher risk for heart disease and stroke associated with the practice.

About 600,000 women in the U.S. have their uteruses surgically removed each year. About half of these procedures include removal of the ovaries.

The newly published data from the Women’s Health Study (WHI), which included more than 25,000 women, confirmed that women who had their ovaries removed during hysterectomy developed fewer ovarian cancers than women whose ovaries were not removed.

Keeping ovaries did not appear to be associated with a lower risk for heart disease, osteoporosis, or cancer among the women in the study.

The findings appear in the April 25 issue of the Archives of Internal Medicine.

Choosing Ovary Removal

Ovary removal has benefits for women at high risk for ovarian cancer due to genetic predisposition or family history, and the new analysis appears to tip the scales in favor of removing the ovaries for other women as well.

But it isn’t that simple, experts tell WebMD.

Ovarian cancer is relatively uncommon, while heart disease is the No. 1 killer of older women. More than 10 times as many women die each year from coronary causes as from ovarian cancer.

In the newly published analysis, researchers estimated that one case of ovarian cancer was prevented for every 323 hysterectomies performed with ovary removal.

But keeping ovaries was associated with a clear decrease in heart disease incidence and death from coronary causes in a 2009 analysis of data from the Nurses Health Study (NHS), which included close to 30,000 women.

Health policy researcher Lauren D. Arnold, PhD, MPH, of the University of St Louis, says the contradictory studies can provide a teaching moment for doctors and patients.

“We encourage doctors to practice evidence-based medicine, but that is often interpreted as meaning they need to follow the latest study,” she says. “In this case, we have two very good studies and, for most women, there are still no clear-cut answers.”

Comparing Studies

Two big differences in the studies were the age of the participants and the length of follow-up.

The average age of the women in the Women’s Health Initiative was 63 at enrollment, while women in the NHS trial were enrolled between the ages of 30 and 55. And WHI participants were followed for an average of eight years, while the nurses were followed for 24 years.

NHS researcher William H. Parker, MD, of the University of California, Los Angeles, says the older age of the women in the WHI trial and the fact that the main intent of the study was to examine the impact of hormone replacement treatments on health could have influenced the outcomes.

The surviving women in the NHS trial have now been followed for more than three decades, and Parker says he plans to present an updated analysis within the next two years.

“At this point, like a lot of medicine, the decision about whether to remove ovaries during hysterectomy is an individual one, with each patient bringing her own set of circumstances to the table,” he tells WebMD.

Arnold agrees.

In an editorial published with the study, she and co-author Graham Colditz, MD, of Washington University School of Medicine, write that the subtle differences in the two studies may be easily overlooked by doctors when they counsel patients about the potential benefits and risks associated with ovary removal during hysterectomy.

Arnold says many women facing this decision may not even fully understand that ovary removal is an elective procedure.

“Doctors need to remember that there are no clear-cut answers for most women,” she says.